(1) Field of the Invention
The present invention refers to the catching and bobbin winding of the yarn produced or processed by textile machines.
In the industrial production of yarns, it is customary to process and catch them by winding them onto a tube to form bobbins, which are then transferred to subsequent processing steps and for use.
After effecting these processes on the yarn, there is a significant amount of fluff, i.e. fibers which are not well twisted into the yarn body with the result that one of their ends protrudes therefrom. For some of the subsequent processing operations or use of the yarns, such as spooling or various kinds of weaving, this fluffing can be an obstacle for the processability and/or harmful for the quality of the end product, and must therefore be removed or reduced before use. Said fluffing is normally attributed to the incomplete twist and retention of the fibers in the yarn body, and to the fact that it is induced by the same processes effected on the yarn, during which it is in contact with other elements and is subjected to mechanical strains, such as contacts, impact, wipings, abrasions, de-torsions, deviations, centrifugal forces and so on, as well as to effects and stress of the electrostatic or pneumatic type.
A considerable increase in the fluffing of yarn under processing can generally be observed, along its run from the feeding pirn to the winding bobbin of the purified yarn, during yarn finishing processes, or during crosswinding in automatic crosswinding machines for purifying the yarn from its defects. Crosswinding is in fact effected by processing the yarn at high linear rates, normally around 20–30 m/sec, and the mechanical stress on the yarn is normally thought to be the reason for an increase in fluffing. In general terms, the higher the winding rate, the higher the increase in fluffing during the run of the yarn from the pirn to the bobbin. For this reason, fluff suppressing devices have been proposed in the state of the art, to be inserted along the run of the yarn of automatic crosswinding machines.
(2) Description of Related Art
A fluff suppressing process is presented in U.S. Pat. No. 5,263,311 in the name of the Institute of Textile Technology. This process reduces the fluffing of spun yarn by inducing, along the yarn, an air vortex with an axial component opposite to the yarn direction. The vortex rotation is directed in a counter direction to the twist of the yarn. A fluff suppressing device of analogous concept is presented by U.S. Pat. No. 5,351,472 in the name of Murata. This device also operates by means of air vortexes on the yarn, in a cylindrical duct having a longitudinal slit for the insertion and disinsertion of the spun yarn.
Nozzles are positioned on said cylindrical duct, for injecting air in a tangential direction with respect to the passage of the yarn, as well as control means of the balloon induced on the yarn, for containing and controlling it in its longitudinal extension at the duct outlet.
According to the subsequent patent application EP 1,013,803 in the name of Murata, the fluff suppressing device is equipped with a closing mechanism of the tangential slit for the yarn insertion. Sucking means are also envisaged in the duct—in addition to the blowing nozzles—to remove powder and short fibres, detached by the action of the blowing nozzles, from the spun yarn already inside the duct itself.